American Board of Ophthalmology (ABO) Practice Exam 2025 – The Complete All-in-One Guide to Exam Success

The cranial nerve responsible for most eye movements is cranial nerve III, also known as the oculomotor nerve. This nerve innervates the majority of the extraocular muscles, which are essential for the movement of the eyeball. Specifically, it controls the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles, allowing for a wide range of eye movements such as up, down, and inward.

Additionally, cranial nerve III is also responsible for controlling the constriction of the pupil and maintaining the eyelid position, which are important aspects of oculomotor function. This extensive role in both eye movement and ocular function is what makes cranial nerve III the primary nerve associated with most eye movements.

In contrast, the other cranial nerves listed have more limited functions. Cranial nerve II is primarily responsible for vision, cranial nerve IV (the trochlear nerve) controls the superior oblique muscle for downward and inward eye movement, and cranial nerve VI (the abducens nerve) controls the lateral rectus muscle, which is responsible for outward eye movement. Each of these nerves plays a role in eye movement, but they do not contribute to the same extent as cranial nerve III